1. Field of the Invention
The present invention relates to a reflector for lights of higher power, which comprises a base body made of glass or glass ceramic, which has a receptacle for a lamp, preferably a high pressure gas discharge lamp, an interior mirror surface and an outer surface provided with a jacket.
2. Description of the Related Art
The term “light” means a device for receiving and for operating a commercial light source (gas discharge lamp, light bulb, etc) for the purposes of the present invention. The present invention generally concerns those lights, which have an optical reflector to provide the desired distribution of light, such as lights in the home, lights for supplying light to a light guide, auto headlights, projectors, etc. This sort of reflector generally has an elliptical, parabolic or conical section basic shape. It can contain glass or glass ceramic as a substrate. Typically it has a so-called cold light mirror, with which the visible radiation of the built in lamp is reflected and through which the IR radiation passes. The reflector thus has a colored residual exterior transmission, usually blue, but also red, green or other colors.
This sort of reflector is widely used by the lighting industry, especially in freely hanging halogen lights for room illumination. The associated lamps have a comparatively lower electrical power, in a range of 10 to 60 watts.
However there are also lighting units with reflectors, which require light sources with higher electrical power, for example digital projectors, so-called beamers, headlights, etc. The power of these lighting units is in a range of 200 to 400 watts. Light sources or lamps for these lighting units with reflectors are typically gas discharge lamps. They have a high interior pressure of up to 2×105 hPa. They have numerous technological advantages however their service life is limited by thermochemical influences. Generally the service life of these lamps is of the order of 2000 hours.
The present invention especially concerns reflectors for this sort of light of higher power.
A serious disadvantage of these gas discharge lamps is that at the end of their service life an explosion destroys them. This explosion seriously damages the reflector, produces flying glass splinters and pieces and causes considerable damage. This explosion also can damage valuable optical components and parts of associated equipment.
To avoid glass splinter formation reflectors are made with greater wall thickness. Their wall thickness is more than 4 mm. However thermal expansion of these reflectors again leads to breakage because of the high heat load. Increasing the reflector wall thickness is thus not a satisfactory solution.
There is an additional problem. In order to mask or screen scattered light from the reflector, commercially obtained reflectors are surrounded by a housing, which has aeration slots for heat dissipation, from which light issues, which can be troublesome. In order to keep the aeration slots small, fans must be already provided. Noise generation is associated with the operation of these fans.
A reflector for a high pressure gas discharge lamp is known from DE 100 24 469 A1, which has explosion protection means and a light protector, so that no housing with aeration slots and only a reduced cooling by fans are required.
The known reflector has a protective jacket around its exterior circumference, which comprises a coating of heat-resistant viscous plastic, preferably a fluoro-polymer, which can be formed for deflecting light, which occurs typically by additional application of an lacquer layer.
It has been shown that the plastic coating does not guarantee explosion and splinter protection, since tears or fractions are formed because of great thermal load and larger splinters that can arise during explosion of the high-pressure gas discharge lamp. Furthermore a second coating is necessary in practice, in order to guarantee light protection.